Page Break Problem In Post

Hi

I’m unable to break a post page with long content, using WP 2.8, i tried <!--nextpage--> in my post but the content after <!--nextpage--> tag get invisible nor it shows any link to view the rest.

Here i go with my page.php code

<?php
get_header(); ?>
<div id="content">
<div id="page-meta" class="clearfix">
</div><!-- End page-meta -->
<div id="page-content">
<?php if (have_posts()) : ?>
<h2 class="pagetitle"><?php the_title(); ?></h2>
<?php endif; ?>
<ul id="posts" class="clearfix">
<?php if (have_posts()) : while (have_posts()) : the_post(); ?>
<li <?php post_class( 'single' ); ?>>
<div class="post-content">
<?php the_content(); ?>
<?php wp_link_pages(array('before' => '<p><strong>Pages:</strong> ', 'after' => '</p>', 'next_or_number' => 'number')); ?>
</div><!-- End post-content -->
</li><!-- End post -->
<?php endwhile; endif; ?>
</ul><!-- End posts -->
</div><!-- End page-content -->
<?php include( TEMPLATEPATH . '/ad-footer.php' ); ?>
</div>
<?php include( TEMPLATEPATH . '/copyright.php' ); ?>
</div><!-- End col-64 (Left Column) -->
<div class="col-278 right">
<?php get_sidebar(); ?>
</div><!-- End col-278 (Right Column) -->
<?php get_footer(); ?>

also visited http://codex.wordpress.org/Styling_Page-Links and tried several options like

#1
<div class="pagelink"><?php wp_link_pages('pagelink=Page %'); ?></div>

#2
<?php wp_link_pages('<p>Pages: ', '</p>', 'next', ' &raquo;', '&laquo; '); ?>

Result 0 – Pls Help